Melting magnesium metal and the like



Oct. l, 1946. E. c. LYoNS MELTING MAGNESIUM METAL AND THE LIKE Filed Nov. 9, 1944 INVENTOR.

BY- @IMA gi-W 17km; 1% l I v A-rToRNEYs Patented Oct. 1, 1946 UNITED STATES PATENT OFFICE y Y 1 Y:nuit-,466

MEL'rING mGNEsIUt/ i' METAL AND 'T-HE LIKE Ellis C.'Lyons, Boulder City, Nev., assigner, by mesne assignments, to Reconstruction Finance Y Corporation, a corporation of theUnited Statesl 'Application November 9, 1944, serial No. A562,722

7 Claims. (C1. 266-33) This invention relates to the melting of magnesium and magnesium base alloys, and has for its object the provision of certain improvements in the melting of magnesium and in the melting,

and the production of .magnesium base alloys is customarily carried out at the plant where the magnesium is produced or in plants for refining and alloying magnesium. On the other hand,

magnesium base alloys are customarily remelted l" and cast in foundries for manufacturing Ystructural and other mechanical articles of the alloy. The present invention contemplates an improved apparatus for melting and refining'crude 2 with molten metal and communicates with the elongated molten metal reservoir. In the form of the apparatus particularly adapted for'remelting clean and puried magnesium base alloys, the

aforementioned receptacles are unnecessary for with or without refining, of magnesium and its 5 allOYS- Y settling out impurities, and either or both may be Magnesium is vcommonly produced by the elecl. used for introducing molten metal into the resertrolysis of a fused bath of magnesium chloride or Voir as molten metal is discharged therefrom, or by rreduction of Vmagnesium* oxide. The crude othersuitable means may be provided for-such metal is characteristically contaminated with oxintroduction of molten metal into the reservoir; ide, chloride or other impurities which are cus- The temperature of the fused salt bath may be tomarily removed by remelting and/or rening controlled to maintain the molten metal in the the molten metal. The reiined metal is usually reservo-ir within a predetermined temperature alloyed with other metals to impart desirable Tangehardening and corrosion-resisting qualities there- The foregoing and other novel features of the to for structural and other mechanical and cominvention which I believe to be patenta'ble are mercial uses, as, for example, in the automotive set forth in thev appended claims. The prinand aircraft industries. Among the many magciples of the invention will be best understood nesium base alloys so used may be mentioned, from the following description taken in conmerely by Way of example, the magnesium-alujunction with the accompanying drawing, in minum-zinc-manganese alloys containing 0.1 to which the single gure is a side elevation, partly .12% aluminum, none up to 5% zinc, none up to iny section and somewhat diagrammatic, of an 3% manganese, and the balance essentially magapparatus embodying the invention. nsium- Y f Y `Referring to the drawing, an insulated tank 5 The meltingVV and rening of the crude metal holds a fused salt bath'. The bath 6 may be heated by any convenient means but is preferablyheated by one or more pairs of electrodes 7 electrically connected to a suitable source of electricenergy B thro-ugh a thermostatic control device 9 including a pyrometer ID thermally associated with the bath.

An elongated conduit or molten metal reservoirV I I is submerged in the fused salt bath 6. The conduit is in the form of an oval coil extending magnesium and for melting magnesium-base `al ,-35 from near the top to near the bottom of the bath loys, with or Without refining. In its broad aspect, and is appropriately supported by standards I2. the apparatus of the invention comprises an elon- The upper end of the conduit I I communicates gated molten metal reservoir immersed in a fused with the upper end of an enclosed receptacle or salt bath, with means for introducing metal into settling unit I3 completely submerged in thefused the reservoir under conditions inhibiting oxida- Lio ysalt bath.y A second receptacle or settlingunit tion, and with a Valve-controlled discharge for Ul is immersed in the fused salt bath. The rethe reservoir, the reservoir being so constructed ceptacle I 4 is open at its top, above the level of that in'operation it is iilled with molten metal the bath, and is connected to the receptacle I3' Which flOWS 'by gravity from the point of intro# by a conduit I5 at a level slightly below the comduction thereto to the point of discharge there# munication of the receptacle I3 with the elo-nfrom. In the form of the apparatus 10211131011- gated conduit II. The conduit I5 may advanlarly adapted for use in melting and rehng tageously slope upward from the receptacle I4 crude magnesium, the melted metal iS held in tothe receptacle I3. The receptacle Id has ardetwo receptacles immersed Vin the fused salt bath pending drain |5 with a, discharge valve :1 a1; and communicating with each other beneath the the bottom. thereof The receptacle |3 has a.

molten metal level, and in' which impurities are` permitted to settle out. One of the receptacles may be open to the atmosphere and the crude metal introduced into the top thereof. The other receptacle may be completely enclosed and is lled similar depending drain IAB with a discharge valve i9. A heating coil 2o surrounds the lower end of each drain I5 and I8, exteriorly of the bottom of the tank 5, to prevent freezing of the metal and impurities in the drains. The lower end of the elongated conduit II communicates with a discharge conduit 2 I having a valve-controlled metal outlet 22. The conduit 2| and Valve outlet 22 may be heated to prevent freezing of the metal.

The apparatus illustrated in the drawing is particularly adapted for magnesium refinery operation. Molten metal, solid pigs or shapes, scrap, and the like may be advantageously treated in the apparatus to separate therefrom the associated impurities such as particles of salt (cell melt), flux, oxides etc. which may contaminate the crude metal. The crude or contaminated metal to be treated, for example the pig 23 illustrated inthe drawing, is introduced into the open upper end of the settling unit I4. Solid metal so introduced is melted by the heat of the fused salt bath. The impurities, being heavier than the molten magnesium metal, settle towards the bottom of the unit I4 and may be removed from time to time through the discharge valve I1 of the drain I6. Further settling of impurities takes place in the settling unit I3 and may be removed from time to time through the discharge valve I 9 of the drain I8. Substantially pure metal-is delivered from near the top of the settling unit I3 lto the elongated conduit Il.

The fused salt bath is thermcstatically controlled to bring the molten metal in the elongated conduit II to the proper casting temperature. This vcan be accurately accomplished in the apparatus of the invention, since the salt bath assures uniform heating of the metal in the conduit within narrow ytemperature limits. Purified molten metal is withdrawn from the conduit II, as required for casting, through the outlet 22. Casting may be carried out in sand molds, permanent molds, or the like. Except for the open charging .top of the settling unit I4, the parts of the apparatus holding molten metal are completely enclosed, and the molten metal is effectively protected against oxidation or other contaminating influence. The conduit II is at all times completely f1lled with molten metal, and `the contemplated flow of molten metal through the apparatus results from the action of gravity.

The elongated conduit or molten m-etal reservoir I I may be made of steel, such as ste-el pipe. Such a metal conduit submerged in the fused salt bath has little tendency to scale, rust, pit or corrode, and hence has a long life. Similarly, the receptacles I3 and I4 and conduit I5 may be made of steel.

The fused salt bath may be heated in any appropriate manner, the electrodes and associated devices being described and illustrated merely by way of example. Thus, electric resistance units, submerged pipes through which hot gases pass, etc. may be substituted for the electrodes.

The invention while particularly adapted for treating magnesium and alloys thereof, may be employed with advantage in treating other easily oxidized metals.

,I claim:

l. An apparatus of the character described comprising an elongated and substantially closed molten metal reservoir submerged in a fused bath without communication between the interior' of said reservoir and the material of said bath, means operatively associated with said bath for maintaining the molten metal in the reservoir within a predetermined temperature range, a valve controlled discharge means operatively connected to one end of said reservoir, and means operatively associated with the other end of said reservoir for introducing molten metal into the reservoir when molten metal is discharged from the reservoir.

2. An apparatus of the character described comprising an elongated and substantially closed molten metal reservoir submerged in e. fused bath without communication between the interior or said reservoir` and the material of said bath, a settling unit submerged in said bath and communicating near its upper end with one end of said reservoir and having a discharge in its bottom for settled matter, a Valve controlled discharge means for the other end of said reservoir, and means for heating said bath.

3. An apparatus of the character described comprising an elongated and substantially closed molten metal reservoir submerged in a fused bath without communication between the interior of said reservoir and the material of said bath, a settling unit submerged in said bath and communicating near its upper end with one end of said reservoir and having a discharge in its bottom for settled matter, a valve controlled discharge means for the other end of said reservoir, said reservoir being so constructed that in operation it is filled with molten metal which flows by gravity from the end communicating with said settling unit to said discharge means, and means operatively associated with said bath for heating the same and maintaining the molten metal in said reservoir within a predetermined temperature range.

el. An apparatus of the character described comprising an elongated and substantially closed molten metal reservoir submerged in a fused bath without communication between the interior of said reservoir and the material of said bath, a settling unit submerged in said bath and communicating near its upper end with one end of said reservoir and having a discharge in its bottom for settled matter, a second settling unit open at its top and for the most part submerged in said bath and having a discharge in its bottom for settled matter, said settling units communicating with on-e another intermediate their ends, a Valve controlled discharge means for the other end of said reservoir, and means for heating said bath.

5. An apparatus of the character described comprising an elongated and substantially closed molten metal reservoir submerged in a fused bath without communication between the interior of said reservoir and the Ymaterial of said bath, a settling unit submerged in said bath and communicating near its upper end with one end of said reservoir and having a discharge in its bottom for settled matter, a second settling unit open at its top and for the most part submerged in said bath and having a discharge in its bottom for settled matter, a valve discharge means for the other end of said reservoir, said settling units communicating with one another intermediate their ends `and below the communication of said reservoir with the first mentioned settling unit, said reservoir being so constructed that in operation it is iilled with molten metal which flows by gravity from the end communicating with said first mentioned settling unit to said discharge means, and means for heating said bath.

6. An apparatus for melting an easily oxidized metal comprising an elongated and substantially closed molten metal reservoir submerged in a fused Ibath without COmmunication between the interior of said reservoir and the material of said bath, onevend of said reservoir being adapted to receive molten metal melted rby the heat of said bath, and a Valve-controlled discharge means for the other end of said reservoir, said reservoir being so inclined that molten metal owstherethrough by gravity. f y

7. An apparatus for melting an easily oxidized metal comprising an elongated and substantially closed molten metal reservoir submerged in a rfused bath withoutcommunication between the 10 

